The objectives of this proposal are: 1) to complete elucidation of the pathway to allo bile acids rom cholestanol, a ubiquitous companion of cholesterol and a sterol synthesized in the intima of the atherosclerotic artery. 2) to investigate the details of 12 alpha-steroid hydroxylation in relation to formation of 5 alpha-and 5 beta-bile acids. 3) to assay 12 alpha-hydroxylase from liver samples of humans of all ages in an effort to correlate with an early diagnosis of atherogenesis. 4) to ascertain the biological importance of allo acids and their conjugates to the animal organism. 5) to identify acidic biliary metabolites from dietary sterols. 6) to develop improved syntheses of allo acids, locate natural sources of these materials, and increase sensitivity of methods of detection, separation and identification by such means as computorized mass spectrometry, high pressure liquid chromatography, and high resolution NMR spectroscopy.